The present invention is directed to connectors for power distribution cables, and methods for use of the connectors.
A variety of techniques have been developed for terminating or splicing high voltage cables in the field. High voltage cables are used for distributing power, and can vary in size from #4 gauge up to over 3,000 MCM.
One technique commonly used is a compression crimp with a metallic sleeve. However, there are problems with compression crimps. For example, heavy hydraulic crimping tools are required, which can weigh 50 to 100 pounds. These heavy tools are awkward to use in the field. In addition, a large number of dies are required because a die is needed for each cable size. If the die size is off by even a small fraction, which easily occurs due to die wear, the tool does not perform satisfactorily and crimp failure can result.
Another problem with compression crimps is lack of reliability, especially with aluminum conductors. If an unsatisfactory crimp is formed, the termination or splice can overheat which can result in a fire, system failure, and a blackout.
When a compression crimp is used, often the crimp is filled with a conductive grease to insure better electrical contact and to prevent oxidation. In the field, this conductive grease is very messy. At high temperature the grease can flow resulting in poor electrical contact.
Another problem noted with compression crimps, particularly for aluminum conductors, is that cold flow occurs due to thermal cycling. This can result in a thermal runaway which can cause a fire.
Another technique for forming terminations and splices that has been used is sweating, where hot molten solder is poured into the termination or splice. This also is a very difficult technique to use in the field. A hot tub of solder is required, which creates safety hazards and there are significant losses of expensive solder. Further, temperature control is essential to a good splice or termination, and is difficult to achieve in the field. If the temperature is too low, a satisfactory connection does not result due to a poor metallurgical bond. If the temperature is too high, flux in the solder degrades, resulting in a brittle connection which can fail. Hence, there is considerable worker skill required.
Another technique that has been considered is a chemical heating system, known under the tradename Cadweld, for welding conductors together using an exothermic reaction and molten aluminum. This technique has achieved only limited use because it can be dangerous, it involves a gas which needs venting which is difficult in the field, and it is expensive because the molds used wear out after only fifty uses.
One further technique that has been considered is metal inert gas (MIG) welding, that is welding the aluminum conductors under inert gas to prevent oxidation of the aluminum. This technique requires expensive equipment which is generally unsuitable for field use in that it weighs several hundred pounds or more and is not easily portable.
In view of these problems, there is a need for a method for connecting high voltage electrical conductors that is safe, easy to use, and reliable. There is also a need for connectors to be used in the method.